100% fresh air is delivered into the office spaces through a raised access floor using a system known as displacement ventilation. This type of system achieves much higher air quality and lower energy use than a typical mixed ventilation system. Air enters at floor level and moves slowly along the floor until rising in a plume generated by occupants or other heat sources. Fresh air is thus selectively delivered where needed, and stale air rises past the occupied level, where it moves along the ceiling to an outlet. In this case it exits via the North Atrium into the Solar Chimney. Using the North Atrium as an exhaust collector, the un-tempered atrium space is made comfortable year-round.
Thanks to the radiant heating and cooling system, the ventilation system need only supply enough fresh air to maintain air quality as opposed to conventional HVAC systems, which need to provide air for space heating. This saves fan energy, compared with air-based heating systems that circulate up to four times more air through narrow duct work.
The system also eliminates conventional ductwork and a hung ceiling altogether since air enters below the floor and moves through occupied space in an orderly, stratified manner. The lack of suspended ceilings allows for raised window heights, which improving daylight penetration and expose the underside of the floor slab for radiant heating and cooling. Furniture and demountable interior partitions are installed shy of the ceiling in order to maintain free air movement at this upper exhaust strata level (approx. 750mm deep).
Winter-mode air flow rate, for each tower floor, is approximately 6500m³/hour (3800CFM) into the North Atrium through automated glass louvers in the interior curtain wall that separate the office from the atrium space. Not only does the flow pattern improve air quality, but a higher rate of fresh air is in fact necessary, owing to certain limiting factors inherent to the displacement ventilation system. One is air motion: at too low a flow rate, air feels stagnant, and odours linger. The other is air distribution: because the fresh airstream flows directly to occupants (and other heat sources), with each successive occupant the stream is reduced in size, and could be completely used up, leaving downstream occupants without any fresh air. While the higher fresh air rate requires more heating, the system still reaps an overall energy savings, not only by reducing fan energy but also by delegating space heating to the highly efficient radiant system.
Related Performance Goals:
Energy Performance-Sustainable Design
Terms and Conditions
Copyright © 2009. KPMB